1. Field of the Invention
The present invention relates generally to apparatus for inserting and positioning vascular catheters within a patient's vascular system. More particularly, the present invention relates to the construction of a guiding catheter having controlled flexibility and a soft tip.
Arteriosclerosis, also known as atherosclerosis, is a common human ailment arising from the deposition of fatty-like substances, referred to as atheroma or plaque, on the walls of blood vessels. Such deposits occur both in peripheral blood vessels that feed the limbs in the body and coronary blood vessels which feed the heart. When deposits accumulate in localized regions of a blood vessel, blood flow is restricted and the person's health is at serious risk.
Numerous approaches for reducing and removing such vascular deposits have been proposed, including balloon angioplasty where a balloon-tipped catheter is used to dilate a region of atheroma, atherectomy where a blade or other cutting element is used to sever and remove the atheroma, and laser angioplasty where laser energy is used to ablate at least a portion of the atheroma. Catheters can also be introduced to the vascular system for imaging, arrythmia mapping of the heart, defibrillation of the heart, and for a variety of other diagnostic procedures.
With all such techniques employing interventional and diagnostic catheters, it is necessary to properly locate the catheter so that the interventional or diagnostic element (usually at the distal tip of the catheter) is located at the region to be treated within the vascular system. As the catheters can be percutaneously introduced at locations quite remote from the region of atheroma, it is frequently necessary to maneuver and manipulate the catheter through various branches and regions within the vascular system.
One method for positioning vascular catheters utilizes guiding catheters. Such guiding catheters are elongated flexible tubes having a central lumen to accommodate the interventional or diagnostic vascular catheter to be introduced. Often, the guiding catheter will have a bent or curved tip to facilitate placement in a particular region of the vascular system, and positioning can be accomplished under conventional fluoroscopic imaging. Once the guiding catheter is in place, a diagnostic or imaging catheter can be introduced through the central lumen to the desired treatment location within the vascular system.
To be successful, the guiding catheter must satisfy a number of competing demands. The guiding catheter should be sufficiently flexible to permit introduction through the vascular system, particularly through the coronary arteries. The catheter should also be sufficiently axially rigid (i.e. have sufficient column strength) so that it can be pushed forward through the vascular system without kinking and collapse. Desirably, the catheter will have a controlled flexibility along its length to meet both these demands. The catheter should further have sufficient torsional stiffness so that the distal end can be turned (to properly orient the curved tip) by rotating the proximal end which remains accessible to the physician. The catheter should further have a relatively soft tip, to avoid injury to the blood vessel during initial placement. The catheter should still further be strengthened in the regions where it is curved or bent, as these regions are generally more prone to collapse. Catheter construction should also accommodate the placement of side holes or ports which permit perfusion of blood through the central lumen when the catheter is in place. Moreover, the catheter should be able to meet all of these mechanical demands while maximizing the cross-sectional area of the central lumen, i.e., minimizing wall thickness, to accommodate the interventional or diagnostic catheter, permit fluid infusion, and the like.
While previous guiding catheters have generally been able to meet at least some of these requirements, others have remained unmet. It would therefore be desirable to provide guiding catheters which meet at least most and preferably all of the above requirements with a minimum of compromise.
2. Description of the Background Art
U.S. Pat. No. 4,817,613, discloses a guiding catheter having an inner lubricous sleeve, a braided torque transmitting member, and a plastic material impregnated into the braided torque transmitting member. Other guiding catheters employing braided reinforcement layers are described in U.S. Pat. Nos. 4,425,919; 3,924,632; and 3,416,531; and Cook, Inc., Radiology, Cardiology, & Surgery Catalog (1982-84). The disclosures of each of these references is incorporated herein by reference.
Referring to FIGS. 1 and 2, a prior art guiding . catheter 10 which has been commercially available from Devices for Vascular Intervention, Inc., assignee of the present application, includes a catheter body 12 constructed generally in accordance with U.S. Pat. No. 4,817,613, described above. The catheter body 12 includes an inner lubricous liner 14, a braided torque transmitting member 16, and a plastic material 18 impregnated into the torque transmitting member 16. A soft tip 20 extends over the distal approximately 2 mm of the inner lubricous liner 14 and lies adjacent to the termination of the braided layer 16. Side perfusion ports 22 are formed through the wall of the catheter body 12, penetrating the lubricous layer 14, the braided layer 16, and the impregnant layer 18. A stainless steel support ring 23 is provided in the region of the perfusion ports 22.